1. Field of the Invention
This invention relates to a quick release device for a bicycle, more particularly to a quick release device used in tightening a hub assembly of a bicycle to left and right fork blades.
2. Description of the Related Art
Referring to FIGS. 1 to 3, a quick release apparatus 10 for a bicycle as disclosed in U.S. Pat. No. 5,622,412 is shown to include a drawbar 11, a housing 12 sleeved on a cam follower member 111 of the drawbar 11, a rotary cam 13 extending perpendicularly to the drawbar 11 and mounted rotatably between the cam follower member 111 and the housing 12, a cam lever 14 coupled to the rotary cam 13 and extending outwardly of the housing 12, and an adjusting bolt 15 screwed to a thread end segment 113 of the drawbar 11.
The rotary cam 13 has a large diameter portion 131, an eccentric cam portion 132 extending axially from the large diameter portion 131, a small diameter portion 133 extending from the cam portion 132 and coaxial with the large diameter portion 131, and a control shank 134 extending axially from the small diameter portion 133. When the rotary cam 13 is inserted into the housing 12 and the cam follower member 111, the cam portion 132 is received in a through hole 112 in the cam follower member 111 such that the control shank 134 is meshed with a toothed hole 141 in the cam lever 14.
In use, when the cam lever 14 is rotated, the cam portion 132 presses the cam follower member 111 to move the drawbar 11 axially so as to tighten or release left and right fork blades 21 of the bicycle to or from a hub assembly 20. However, since the rotary cam 13 is driven to rotate by the cam lever 14 from one side, and since the driving force is concentrated at the control shank 134, the force borne by the rotary cam 13 is not evenly distributed, thereby resulting in wobbling of the rotary cam 13 during the process of rotation. Thus, operation of the conventional quick release apparatus 10 is neither stable nor smooth. Furthermore, due to wobbling of the rotary cam 13 during the rotation process, the precision of movement of the drawbar 11 will be adversely affected.